The air intake system for a heavy duty vehicle engine usually includes a relatively large heavy duty air cleaner which may be mounted remote from the engine, and an air intake tube which communicates ambient air into the air cleaner. In order to prevent rain and other foreign material from entering the air intake tube and thereby gaining access to the air cleaner when the vehicle is operated under adverse conditions, a rain hood is provided at the open end of the intake tube. Conventional heavy duty vehicle air intake systems have air intake tubes of at least seven different diameters, thereby requiring seven different models of rain hoods in order to accommodate each of the seven different sizes of air intake tubes. Obviously, this situation provides an inventory and stocking problem for manufacturers and distributors of air intake system components.